Optical fiber, optical device, and method for manufacturing optical device

Abstract

An optical fiber includes a core, a helical section in which the core has a helical shape, and a first end part that is included in either a first non-helical section in which the core has a linear shape or a first gently helical section in which a total number of helices of the core per unit length is smaller than that in the helical section.

1 . An optical fiber comprising:
 a core;   a helical section in which the core has a helical shape; and   a first end part that is included in either:
 a first non-helical section in which the core has a linear shape,
 or 
 
 a first gently helical section in which a total number of helices of the core per unit length is smaller than that in the helical section. 
   
     
     
         2 . The optical fiber according to  claim 1 , wherein the optical fiber in the helical section is connected to the optical fiber in the first non-helical section or the first gently helical section. 
     
     
         3 . The optical fiber according to  claim 1 , wherein the helical section is continuous with the first non-helical section or the first gently helical section. 
     
     
         4 . The optical fiber according to  claim 1 , further comprising:
 a second end part that is included in either:
 a second non-helical section in which the core has a linear shape, or 
 a second gently helical section in which a total number of helices of the core per unit length is smaller than that in the helical section. 
   
     
     
         5 . The optical fiber according to  claim 4 , wherein the optical fiber in the helical section is connected with the optical fiber in the second non-helical section or the second gently helical section. 
     
     
         6 . The optical fiber according to  claim 4 , wherein the helical section is continuous with the second non-helical section or the second gently helical section. 
     
     
         7 . The optical fiber according to  claim 1 , wherein the helical section is longer in length than either of the first non-helical section or the first gently helical section. 
     
     
         8 . The optical fiber according to  claim 1 , wherein the helical section is shorter in length than either of the first non-helical section or the first gently helical section. 
     
     
         9 . The optical fiber according to  claim 1 , wherein the helical section includes, in an alternating pattern, a section in which the core turns right and a section in which the core turns left. 
     
     
         10 . The optical fiber according to  claim 1 , further comprising:
 a clad surrounding the core, wherein   in the helical section, a center of the core is spaced from a center of the clad.   
     
     
         11 . The optical fiber according to  claim 1 , further comprising:
 one or more additional cores.   
     
     
         12 . The optical fiber according to  claim 11 , wherein the core in the first non-helical section or the first gently helical section has an effective refractive index higher than that of the core in the helical section. 
     
     
         13 . The optical fiber according to  claim 1 , wherein the first end part of the optical fiber is attached to a structure configured not to rotate. 
     
     
         14 . An optical device comprising:
 the optical fiber according to  claim 1 ; and   one or a pair of fan-in/fan-out devices connected with one end or both ends of the optical fiber.   
     
     
         15 . A method for manufacturing an optical device, comprising:
 cutting an optical fiber including a core in a gently helical section, wherein the optical fiber has a helical section in which the core has a helical shape and the gently helical section in which a total number of helices of the core per unit length is smaller than that in the helical section.